The Longmenshan Fault Zone is located in the eastern margin of the QinghaiTibet Plateau. By processing， interpreting and inversing the magnetotelluric observation data which were obtained in 2007 from the SongpanZhongjiang profile through the middle of Longmenshan tectonic zone, this paper reveals 30 km deep crust architecture of SongpanGanze foldbelt, Longmen Mts and Western Sichuan foreland basin, and finds the westinclined the highconductivity layer in the crust of 10~20 km of Longmen Mts., it is estimated to deep conductivity characteristics of thrustbelt structure in Longmen Mts.. Sichuan basin, the east of Longmen Mts., which has the characteristics of under the upper thick low resistance sedimentary is the stable high resistance bedrock block. The west of it is SongpanGanze foldbelt, which in upper Paleozoic is high resistance rock mingled with low resistance fragments, the lower crust represent continuous low resistance, to speculate there may be a continuous and stable highconductivity layer shell. Resulting from SongpanGanze foldbelt thrust in the Sichuan Basin stability block, Longmen Shan Fault Zone formed opportunely the unique geoelectrical structure which is a high resistance in the upper and lower part of high resistance basin basement, and mingling with low resistance zone in the middle. It is that the Wenchuan earthquake belongs to the dextialreverse faulting type.